Drafting machine



April 25, 1939. c. H. LITTLE DRAFTING MACHI NE Filed March 25, 1935 4 Sheets-Sheet 1 m m gm ATTORNEYS April 25, 1939. c. H. LITTLE DRAFTING MACHINE 4 Sheets-Sheet 2 INVENTOR. CHARLES /7. [/7745 Filed March '25, 1935 49% ATTORNEZSC April 25, 1939.

C. H. LITTLE DRAFTING MACHINE Filed March 25 1935 4 Sheets-Sheet 4 Fic; I0

INVENTOL OM04 b! LITTLE ATTORNEYS.

Patented Apr. 25, 1939 UNITED STATES PATENT OFFICE D'RAFTING MACHINE Application March 25,

9 Claims.

The present invention relates to drafting machines and more particularly to drafting machines of the type wherein a plurality of connected parallelograms of the band type are employed to maintain parallelism of one or more rulers, etc., as the same are moved about a drawing board or table.

Heretofore in the art, this type of machine has been made with thin, hardened steel bands, en-

circling equal diameter wheels, and held taut under heavy pressure. In order that the arm will move easily, the bands are made thin and of small cross section (.020" x so that they will pass around the pulleys or wheels without undue resistance and can be kept taut without too much stress (about 100 pounds). In operation the pressure of a pencil point on the edge of the ruler attached to the protractor stretches this band on one side, and throws the ruler out of alignment. There is also danger of personal injury in the event the band snaps under the one hundred pound tension to which it is subject, due to crystallizing of the metal by its alternate motions about the wheels or pulleys.

The principal object of this invention is to retain the accuracy and other advantages of the thin steel band, while greatly increasing its holding power by encircling the same with one or more steel cables or wire cords. Two steel :0 cables have a combined breaking strength of four thousand pounds, and when placed outside the steel band increases the holding power of the band many times, practically holding the rulers in perfect alignment when pressed by a pencil.

The cable or cables also give an excellent safety feature, holding the fiat steel band from flying, or an end of it from flying, if it snaps. The cable will not snap. When the cable is old, separate wires may break but they will not fly. The cable 4,0 or cables give very little resistance to passing around the pulleys and require very little tension to keep the same taut. It will thus be seen that this compound band comprising a flat steel band and one or more steel cables outside of the steel band gives accuracy, great holding power against, or resistance to, change of alignment of theruler under pressure, safety from personal injury, and low stresses in the arm.

Another object of the invention is the provision of a novel drafting machine which will be light in weight, rugged in construction, and in which the weight of the rulers, protractor, etc., or. at least a part thereof, will be supported from the arm.

66 Another object of the invention is the provi- 1935, Serial No. 12,869

sion of a novel anchor for a drafting machine arm which will permit the arm, including the protractor and rulers to be readily raised from the board, but which will notpermit the arm to raise from the board under its own weight when the elbow thereof has been moved outside the edge of the board or table to which the anchor is attached.

Another object of the invention is the provision of a novel means of attaching the anchor of a drafting machine to the drawing board or table, which will permit the part of the anchor above the surface of the board or table to be readily moved or shifted a small amount, so that it will not interfere with the rulers etc. when working in certain positions onthe board or table.

The present invention resides in certainnovel details of construction, combinations and arrangements of parts, and further objects and advantages thereof will be apparent from the following description of the preferred embodiment thereof described with reference to the accompanying drawings, in which Fig. 1 is a plan of a drafting machine embodying the present invention;

Fig. 2 is a side elevation of the drafting machine shown in Fig. 1;

Fig. 3 is an enlarged view of the anchor end of the drafting machine shown in Fig. 1;

Fig. 4 is a side elevation of Fig. 3, looking toward the right;

Fig. 5 is a rear elevation of Fig. 3

Fig. 6 is a section approximately on the line 66 of Fig. 3 with the protractor parallelogram of the parallel motion arm rotated Fig. 7 is a section approximately on line 1-4 of Fi 4;

Fig. 8 is a section with portions shown in elevation on the lines 88 of Fig. 1;

Fig. 9 is an enlarged plan view of the protractor end of the drafting machine shown in Fig. 1;

Fig. 10 is a section with portions shown in elevation approximately on line IU-Hl of Fig. 9;

Fig. 11 is a section with portions shown in elevation approximately on the line I l-| l of Fig. 9; 5

Fig. 12 is an enlarged detail view of the takeup or turn-buckle; and

Fig. 13'is an enlarged detail of the band.

Similar reference characters designate corresponding parts throughout the several figures 50 of the drawings.

Referring to the drawings, the drafting machine shown therein comprises a protractor, designated in general by the reference character A, constituting a part of the free end of a parallel u motion arm comprising two parallelograms of the wheel and band type. The upper end of the parallel motion arm is connected to an anchor designated in general by the reference character B, slidably supported on a bracket attached |lzo the upper edge of the drafting board or table The anchor parallelogram of the-parallel motion arm, so designated because it is the parallelogram connected to the anchor, comprises a 'flanged wheel |4 secured to a bracket member I5, which forms a part of the anchor B, by screws l6, a similarly flanged wheel l'l' rotatably supported in the lower end of an adjustable strut C pivotally connected to the center of the wheel M, and a flexible band. designated in general by the reference character D, encircling the wheels Id and I! and engaging the same between the flanges thereof. The adjustable strut C comprises an angular end member l8 connected to a short shaft or rod 9 slidably supported in the end of a tubular rod or shaft 20 which forms the strut proper. and a similar angular member 2| secured to the other end of the shaft 23 in any convenient manner. For the purpose of adjusting the effective length of the strut C and in turn the tension of the band D, the member l8 abuts against the end of an internally threaded sleeve 22 threaded onto the adjacent end of the tubular shaft 23. The lower end of the sleeve 22 is extended and u'nthreaded, the construction being such that the threads on the member 20 are covered in any adjusted position of the sleeve 22.

The upper end of the member l8 which projects over the wheel I4 is clamped between the head of a bolt 28 which projects through an aperture therein and a nut 29 threaded onto the bolt below the member. A pin 33 secured to the head of the bolt and projecting into a suitable aperture in the member l8 prevents relative rotation between the parts. The bolt 28 and in turn the member I8 is rotatably supported in the wheel M by a four point bearing comprising the antifriction members 3|. The upper inside race for the members 3| is formed on the lower edge of the nut 29', the lower inside race on a member 32 threaded onto the bolt 28 and held in any adjusted position by a lock nut 33, and the outside races on the Wheel M. The angular member 2! projects over the upper side of the wheel it and has a short tubular shaft 34 fixed thereto about Which the wheel I! is rotatably supported. preferably by anti-friction bearings.

The band D which encircles the wheels I 4 and I1 comprises a flexible flat metal band 35 the ends of which are welded or otherwise secured together to form a continuous band. and a plurality of cable bands 36 and 31 of flexible cable. preferably airplane steel cable, the ends of which are connected together by turnbuckles or takeups 38 and 39. respectively. The turnbuckles illustrated. see Fig. 12. comprise tapped tubular members All and 4| attached to the ends of the cable in any convenient manner, threaded cnto a central member 42, and are provided for the purpose of adjusting the length of the cable bands with respect to the fiat band, and for distributing the load therebetween. The tubular members 58 and 4| are provided with elongated apertures 43 extending therethrough adapted to receive a tool for the purpose of holding the same against rotation while the threaded member 472 is rotated by a tool inserted in the holes 44. The cable bands 36 and 31 are held in alignment with the fiat band 35 by a plurality of metal clips 45 carried by the cables and provided with projections extending over the upper and lower edges of the flat band 35. The clips 46, which are preferably made of spring steel and snap into place on the cables, permit longitudinal movement of the cable bands with reference to the flat band and, if desired, may be secured against longitudinal movement along the bands in any convenient manner.

The wheel I! is common to both the anchor and protractor parallelograms, see Fig. 8, and the right hand wheel 53 of the protractor parallelogram is built onto or forms a part of the protractor A, see Fig. 10. The band D of the protractor parallelogram is similar to the band of the anchor parallelogram and the construction thereof will not be described in detail. The duplicate parts thereof are indicated by the same reference characters. The left hand angular end member. 52 of the strut C of the protractor parallelogram is adiustably secured to the strut proper in the same manner as the member 8 is secured to the tubular shaft 23, and projects underneath the lower side of the wheel I! to which it is rotatably connected. through the medium of a short tubular member 53 fixed thereto. in a manner similar to the member 2| of the strut C. The members 2| and 52 together with the short tubular members 34 and 53 secured thereto, respectively, are held in assembled relationship with the wheel l! by a bolt 54 projecting through the tubular members 34 and 53 and retained in position by a nut 55 threaded onto the upper end thereof. A washer 55 is preferably interposed between the member 2| and the nut 55. The right hand member 6|! of the strut C extends underneath the wheel 53, and has a short tubular member 6| fixed in an aperture therein. by means of which it is rotatably connected to the wheel 5!! through the medium of an anti-friction four point bearing 62.

The protractor illustrated is especially adapted for civil engineering and navigation work. and, as previously stated. has the center thereof coincident with the center of the wheel 50 at the free end of the parallel motion arm. The protractor proper comprises a washer shaped member or protractor ring 55 rotatably supported in a recess formed in the upper side of a flange 54 integral With the Wheel 53 and adapted to be clamped in any adjusted position by two members 66 spaced apart. The members 66 are slightly underout toward the center of the protractor'and are moved to engage and disengage the member 65 by winged studs 6? threaded into projections 68 on the flange 64 above which the members 66 are supported. A transparent member 69 secured to the flange 64 of the wheel 58. and provided with a zero mark facilitates the adjustment of the protractor ring 65 to any desired position.

The ruler plate 10 to which the rulers 1| and 72 are chucked in a manner similar to that disclosed in my copending application Serial No. 526,912, filed April 1. 1931. and which has matured into Patent No. 2.049.302. is secured to a disk member 13 rotatably supported by the protractor ring 65, through the medium of a cylindrical member 15. A plurality of screws i5 extending through the members 10 and 15 and threaded into a tapped aperture in the member 13 retain the parts in assembled relationship. A hand grasp or knob 78 secured to the disk member 13 facilitates manipulation of the instrument as a whole. and the adjustment or rotation of the rulers etc. about the center of the wheel 50. The disk member 16, and in turn the ruler, is adapted to be secured in any adjusted position by a clamp bolt I9 actuated by a wing nut 80 threaded onto the end thereof.

The protractor and handle both set very low with reference to the drawings, and the protractor ring may be set at any desired angle, which is always shown. This is a very desirable feature in a number of instances, for example, the correction of the compass reading at any particular point may be made by turning the protractor ring to compensate for the correction, after which the readings are direct and the amount of the correction is always clearly shown.

The anchor bracket I5, previously referred to, is rotatably supported on a rod or shaft 81 so that the protractor and arm may be raised from the board or table, and is slidable therealong so that the anchor may be moved to one side or the other as desired. The shaft 8I forms part of a bracket comprising members 82 and 83 secured to the ends thereof and to a rectangular bar 84 secured to the upper edge of the board as by screws 85. The movement of the parallel motion arm toward the board is limited by the engagement of the upper edge of the bar 84 by a roller 86 rotatably supported on a screw 81' secured tothe end of a member 88 pivotally supported on a screw 89 threaded into a tapped aperture in aboss 90 formed on the bracket I5. The angle which the member 88 makes with the bracket I and in turn the distance at which the parallel motion arm, etc., is supported above the board can be adjusted by means of a screw 0| threaded into a projection 92 on the member 88 and provided with a knurled knob for easy manipulation thereof. The movement of the member 88 about the pivot bolt 89 in a clockwise direction, as viewed in Fig. 4, is limited by a second adjusting screw 94 threaded into a projection 95 on the member 88 similar to the projection 90 but extending in the opposite direction.

In order to prevent the bracket I5, etc., from pivoting about the shaft 8| under the weight of the arm when the elbow thereof has been moved beyond the upper edge of the drawing board or table, a projection in the form of a tongue I00 on a member IOI engages in a groove I02 formed in the bar 84, see Fig. 6. The member IN is pivotally supported on a screw I03 secured to the member 88 and when the elbow of the arm is above the board the tongue I00 is disengaged from the groove I02 by the action of a cam I05 carried on the lower end of the bolt 28, see Fig. 4. The cam I05 engages between the rear side of the member I 0| and an upturned end of a member I06 secured to the bottom of the member IOI as by the screws I01. As the cam I05 isfixed to the lower end of the bolt 28 it turns with the parallel motion arm, and the construction is such that the tongue is engaged in the groove !82 in all positions of the parallel motion arm in which there would be any tendency for the drafting machine to rotate under its own weight about the shaft 8| in a counter-clockwise direction, as Viewed in Fig. 4.

While the preferred embodiment of the invention has been illustrated and described, I do not wish to be limited to the particular construction illustrated and described, which may be varied within the scope of the invention. If desired, the two cable bands illustrated could be replaced by a single band encircling the wheels once or a plurality of times. The flat band may be given a slight curvature which would decrease the tension required to maintain the same taut. The friction between the band and the wheels may be increased by coating the inside of the flat band and/or the wheels, with a thin rubber coating or by applying thereto a cork, leather or abrasive surface. Since the cable bands act on a slightly greater diameter than the flat band, a relative movement is produced therebetween and a wearstrip of thin metal, such as brass, etc., may be interposed between the cable bands and the flat band, if desired. The word cable as used throughout the present specification and claims is synonymous with the phrase wire rope, or more technically, possibly, wire cord, and the phrases cable band and cable bands used herein refer to a band or bands made from a length of steel wire cord, the ends of which are connected together in some convenient manner. It is my intention to cover all adaptations, variations, and uses of the present invention which come within the'knowledge of those skilled in the art to which it pertains, and I particularly point out and claim as my invention, the following:

1. In a drafting machine of the wheel and band type, the combination of a plurality of wheels, a strut operatively connected to said wheels for maintaining the same in spaced relation, a flat metal band encircling said wheels, and a wire band encircling said fiat band.

2. In a drafting machine of the wheel and band type, the combination of a plurality of wheels, a strut operatively connected tosaid wheels for maintaining the same in spaced relation, a flat metal band encircling said wheels, a plurality of cable bands encircling said flat band, and means for adjusting the relative lengths of said bands.

3. In a device of the character referred to the combination of a parallel motion mechanism, a stationary member, means for pivotally connecting one end of said parallel motion mechanism to said stationary member for movement about an axis parallel to the plane in which said parallel motion mechanism operates, and means for preventing rotation of said parallel motion mechanism about said pivotal connection for predetermined positions of said parallel motion mecha nism in the plane in which it operates.

4. In a device of the character referred to the combination of a parallel motion mechanism, an anchored member, means for pivotally connecting one end of said parallel motion mechanism to said anchored member, an adjustable stop for limiting the rotation of said parallel motion mechanism in one direction, and means for preventing rotation of said parallel motion mechanism about said pivotal connection for predetermined positions of said parallel motion mechamsm.

5. In a draftng machine, the combination of a parallel motion mechanism, means for pivotally connecting one end of said parallel motion mechanism to a drafting table for movement about an axis parallel to the plane of the table, means actuated by the movement of said parallel motion mechanism for preventing rotation of said parallel motion mechanism about said pivotal connection for predetermined positions of said parallel motion mechanism in the plane in which it operates.

6. In adrafting machine comprising a parallel axis parallel with the plane of the drafting board, and means for preventing rotation of said parallel motion arm about said axis for predetermined positions of the parallel motion arm in the plane in which it operates.

7. In a drafting machine, the combination of a parallel motion arm of the wheel and band type comprising a plurality of pairs of wheels, struts operatively connected to said wheels for maintaining the same in spaced relation, cable bands encircling said wheels, an anchor adapted to be connected to a drafting board or the like, means for pivotally connecting one end of said parallel motion arm to said anchor for rotation about an axis parallel with the plane of the drafting board, means for preventing rotation of said parallel motion arm about said axis for predetermined positions of the parallel motion arm, a member rotatably supported by the wheel at the free end of said parallel motion arm, a second member rotatably supported coaxially with said first mentioned member, and a ruler arm fixed to said second member.

8. In a drafting machine comprising a parallel motion arm of the wheel and band type, the combination of a plurality of wheels, a strut operatively connected to said wheels for maintaining the same in spaced relation, a fiat steel band supplemented by a cable band encircling said wheels, means for adjusting said cable band relative to said steel band, an anchor adapted to be connected to a drafting board or the like, means for pivotally connecting one end of said parallel motion arm to said anchor for rotation about an axis parallel with the plane of the drafting board, an adjustable stop for limiting the rotation of said parallel motion arm in one direction, and means for preventing rotation of said parallel motion arm about said axis for predetermined positions of the parallel motion arm.

9. In a drafting machine, the combination of a parallel motion arm of the wheel and band type comprising a plurality of pairs of wheels, struts operatively connected to said wheels for main taining the same in spaced relation, cable bands encircling said Wheels, an anchor adapted to be connected to a drafting board or the like, means for pivotally connecting one end of said parallel motion arm to said anchor for rotation about an axis parallel with the plane of the drafting board, means for preventing rotation of said parallel motion arm about said axis for predetermined positions of said parallel motion arm, a protractor ring rotatably supported by the wheel at the free end of the parallel motion arm coaxial with said wheel, a second member rotatably supported by said protractor ring coaxially therewith, said protractor ring and said second member being located at the upper side of said wheel, and a ruler arm at the lower side of said wheel fixed to said second member.

CHARLES H. LITTLE. 

